Having accumulated a set of octal tube base clamps, it’s now a matter of selecting the proper clamp for each tube:
The process of shell-drilling the tube base, drilling the hard drive platter, printing a tube socket and case, wiring up the Arduino and base LED, then assembling the whole thing requires a bit of manual labor, assisted by some moderately exotic shop machinery.
The getter flash atop this small 6H6GT dual diode tube rules out a cap and there’s not enough space for a side light:
Fortunately, the base LED completely lights the internal glass:
The slowly changing color would make a fine night light:
It must be Art!